A fiberized adhesive may be applied to a substrate or strand of material using a nozzle having one or more adhesive orifices. One potential application may be in the manufacture of disposable hygiene products or articles. The products typically include a substrate, for example, a non-woven film or non-woven/film laminate material, and another component bonded to the substrate with the adhesive. For example, the fiberized adhesive may be applied to a substrate to attach a waist band to the substrate in the manufacture of a diaper, applied as a positioning adhesive on a substrate in the manufacture of a feminine hygiene product, or applied to secure a core to an outer shell in the construction of hygiene product.
The articles or products may be manufactured by feeding the substrate along the nozzle in a machine direction. The adhesive orifices of the nozzle may be arranged across a width of the nozzle, transverse to the machine direction. Thus, adhesive may be applied over a width of the substrate. In addition, the nozzle may include air orifices positioned between the adhesive orifices in a width direction of the nozzle. The discharged air may oscillate the individual adhesive fibers or strands in width direction as they are applied to the substrate.
It may be desirable to selectively stop and/or start application of the adhesive onto the substrate during manufacture of an article. For example, it may be desirable to provide an intermittent application pattern of the adhesive onto the substrate in the machine direction to allow for gaps either where bonding to the substrate is not desired or to separate adjacent parts or products to be formed from the substrate.
Intermittent application of the adhesive is typically controlled by controlling supply of the adhesive to the nozzle. To provide a gap between adhesive sections on a substrate in the machine direction, the supply of the adhesive to the nozzle may be interrupted, for example, by stopping a metering pump or actuating a valve.
However, in conventional systems, it is difficult to precisely and accurately control application of the adhesive onto the substrate to start and stop at desired positions. For example, residual adhesive in the nozzle may continue to be discharged from the nozzle orifice even after a supply of the adhesive to the nozzle has been interrupted, resulting in an over-application of adhesive to the substrate. This is commonly referred to as overspray, which leads to increased material cost and glue contamination of the product areas that should be free of adhesive. Further still, to improve positioning of the gaps, a line speed of the substrate may be reduced, resulting in increased production time.
In addition, a desired application pattern of the adhesive, as a whole, on the substrate is typically in a rectangular shape, with precisely defined lateral edges (edge definition) and ends where the adhesive starts and stops. With conventional nozzles, it may not only be difficult to precisely control the ends where the adhesive application starts or stops as described above, but to also control application of the adhesive to have a desired edge definition. For example, in conventional systems, with the air outlet or outlets laterally spaced from the adhesive outlets, the discharged adhesive may be pushed by the air beyond a desired lateral edge, again resulting in overspray.
Moreover, in conventional systems, upon startup, a delay may exist between the discharge of the adhesive and sufficient air discharge to fiberize the adhesive. Accordingly, at startup, non-fiberized, or insufficiently fiberized drops of adhesive may be received on the substrate. This may be referred to as “glue strike through.” The non-fiberized drops received on the substrate may contaminate machine rollers as the substrate is fed along the machine.
Accordingly, it is desirable to provide a nozzle assembly having improved fluid startup and cut-off characteristics so that application of a fluid onto a substrate may be more accurately controlled and overspray may be reduced or limited. In addition, it is desirable to operate at increased line speeds while accurately controlling the application of the fluid onto the substrate. Further, it is desirable to provide a nozzle assembly with improved startup adhesive discharge characteristics and better lateral fluid application control.